I am working on a Flare control Package.

I wish to know if it is alright to use a control cable rated for 300/500V to drive a 220Vac relay coil from the PLC. The cable is 1.5 mm2.

Please note this is internal panel wiring. The Cable from the PLC panel to the Electrical panel where the relays are, is rated for .45KV/.7KV. This is the project standard. But the vendor has used 300/500V wiring for internal panel wiring.

Kindly explain the reason if it is not recommended.

regards
Rashid iqbal

 

It is hard to say if it is "alright" or not.

None of us know what requirements there are where this thing is going, nor what standards might apply, or what specifications might be part of the contract.

It will likely work, but whether it is "alright" is an entirely different question.

 

As i have mentioned, the PLC DO drives a Relay, the voltage fee contact is connected to a remote Local Control Panel where there is another relay driving the load.

I hope I am able to give enough details for you to be able to understand the scenario.

 

Rashid,

You need to provide what country you are doing this in and/or what electrical codes apply to you before someone can help you.

William (Bill) L. Mostia, Jr. PE Fellow
SIS-TECH Solutions, LP

Any information is provided on Caveat Emptor basis.

 

I am in China and generally the Codes are translated version of NEC or IEC codes.

I wish to get another clarification. As i mentioned the relays are 24 Vdc coil and the contact is 220Vac. So if we consider that the 24 Vdc wire to the relay are rated for 300/500 V and the contact wire are rated for 450/750. Are they allowed to share the same raceway. Will these control circuits be classified as Class 1 control circuit.

 

> I am in China and generally the Codes are translated version of NEC or IEC codes.

> I wish to get another clarification. As i mentioned the relays are 24 Vdc coil and the contact is 220Vac. So if we consider that the 24 Vdc wire to
> the relay are rated for 300/500 V and the contact wire are rated for 450/750. Are they allowed to share the same raceway. Will these control
> circuits be classified as Class 1 control circuit.

IEC and NEC are substantially different.

For NEC users:

In general -

The voltage on the relay coil does not matter much as long as it is the voltage the coil is rated for.

The voltage on the contacts does not matter much as long as the contacts and the wire insulation is rated for it.

The wire insulation does not matter much either as long as the rating of the insulation exceeds the highest voltage actually present.

Its a class 1 circuit if it meets the requirements found in Article 725. Generally speaking there is not a whole lot of benefit to it being a class 1 circuit other than some wire size issues if it is in a raceway.

Having said all that, there could be specific cases where some or all of this is not so. It is hard to be able to give you specific advice to a question that is not very specific.

 

The primary reasons i raised this question was in regards to the insulation rating.

Inside the Enclosure for the relays the 24Vdc Circuit and the 220Vac circuit is overlapping as explained for a distance of about 1 to 2 feet. In all other parts of the enclosure the 220Vac circuits and the 24 Vdc circuit are segregated. The Cable going to the Field is segregated as per standard.

Secondly i needed a clarification with regards to the NEC 300.3 (C)

Considering my example where the 24Vdc wire is rated for 300/500. The 220Vac circuit wire is rated for 450/750, then since the 24Vdc wire rating is still higher than the Maximum voltage which is 220Vac. Therefore can i conclude that this format is compliant to NEC 300.3(C)

Is it OK to use 300/500V rated insulation wire for 220Vac circuit.

 

> Is it OK to use 300/500V rated insulation wire for 220Vac circuit.

You seem to be mixing IEC, Chinese, and NEC standards together and I am not sure how you can make that work and abide by them all.

However, to answer your specific question, I think you are complying with 300.3 (C) (1).

I think it is highly doubtful that you are compliant with the NEC on the whole though, given the rating on the wire. That is not an NEC wire or conductor rating so it seems unlikely that it is a type of wire/cable/.cord accepted by the NEC.

 

As per the project specification in China we are only required to follow IEC codes. NEC code are only used for reference purposes only.

To be more specific the cables are required to follow IEC-60227.

Kindly answer the question i asked earlier based on the fact that i only have to comply to IEC standard.